Manufacturing automation has continued to become increasingly important as the need to improve factory efficiency and maintain high throughput production lines increases. In the manufacturing of semiconductor products, many processes and tools are needed in order to produce completed products for the market. For example, manufacturing of semiconductor products may include over 400 processing steps involving more than 100 different tools. Furthermore, the process route can include a high level of reentrance in which the same tool or tool types are used. An important aspect in manufacturing automation is material handling. To facilitate material handling, a transport system is often employed to support the production line.
Conventional transport systems used in, for example, semiconductor manufacturing include transport vehicles, such as overhead transport (OHT) for transferring wafers contained in a carrier. The use of such systems, however, requires human interaction. For example, human operators are required to load and unload carriers onto and from the transport vehicles. The presence of human operators increases risk of contamination, risk of human error and labor cost. These factors undesirably drive up manufacturing costs.
It is desirable to improve material handling to lower manufacturing costs and increase manufacturing efficiency.